Various types of lathes are well known in the art for cutting metal and other materials. They are generally characterized by a headstock including a spindle chuck for holding a workpiece and a drive mechanism for rotating the workpiece with respect to a spindle axis. A typical lathe further includes a carriage supporting a tool holding mechanism for selective axial movement parallel to the spindle axis and lateral movement perpendicular to the spindle axis. Modern CNC lathes generally also include a tool changer mechanism comprised of multiple tool holders, where each tool holder is capable of mounting a single cutting tool. The tool changer mechanism enables each tool holder and its mounted cutting tool to be selectively moved into cutting position relative to the workpiece held in the spindle chuck.
A frequently encountered cutting operation requires positioning a cutting tool, e.g., a drill bit, for drilling into the face of the workpiece in precise alignment with the lathe's spindle axis. Various techniques have been employed to achieve precision alignment, often involving significant and costly setup time and special tooling. For example only, U.S. Pat. No. 5,752,706 describes an adjustable tool holder for facilitating the angular and radial aligning of a drill bit with respect to the lathe's spindle axis. The patent teaches use of a dial indicator 18 in FIG. 1 mounted “such that it may be turned about the drill bit 16 to assess angular and radial misalignment”, which may then be reduced by adjusting the tool holder orientation.
In setting up for the cutting operation, it is important to carefully position and orient the cutting tool to minimize alignment errors which could otherwise occur due to the cumulative effect of various errors and/or tolerances, e.g., between a tool holder bore and tool holder face, between the tool holder face and tool changer mounting surface, and within the tool changer positioning mechanism, etc. This careful positioning and orienting of the cutting tool typically requires a considerable amount of setup time by a person skilled in such procedures.